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Caption

Deep vein thrombosis (DVT), Doppler ultrasound scan. The thrombus (clot) blocking the vein (black) is the white mass at lower centre. Clots can be harmful if they break away and are carried to the heart or lungs where they can result in fatality. DVT has been associated with long haul flights in which the traveller sits still in cramped conditions for long periods of time. This is commonly called economy class syndrome.